Longitudinal drive shaft for motor vehicles

ABSTRACT

A longitudinal drive shaft for motor vehicles, for transferring a torque, consists of two or more shaft sections which are connected with one another by way of an intermediate shaft or a journal. The intermediate shaft or the journal is the carrier of a center bearing and is connected to the shaft section by a homokinetic displacement joint rigidly disposed in a pipe. The parts of the center bearing and shaft sections that are displaced in a crash are configured to be smaller than the inside diameter of the pipe. The inside diameter of the outer joint ring is greater than the outside diameters of the roller bearing of the center bearing and of the pipe. The homokinetic displacement joint is sealed off with a sealing cap and a sealing bellows in the direction of the shaft section, and has a closure lid assigned to it.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a longitudinal drive shaft for transferring atorque in motor vehicles, consisting of two or more shaft sections and ajoint, in which the shaft sections are connected by an intermediateshaft or a journal.

2. The Prior Art

Such longitudinal drive shafts are generally known and serve to transfera torque and are configured so that in a frontal collision or a crash inthe longitudinal direction of the vehicle, the longitudinal shaftshortens in the axial direction, in order to prevent bending out andpenetration into the interior of the vehicle. At the same time, injuriesto passengers are precluded to the greatest possible extent. Alongitudinal drive shaft for motor vehicles of the type described abovehas become known from German Patent No. DE 43 44 177 C1.

This longitudinal drive shaft for motor vehicles has an intermediatejoint that is configured as an axially displaceable ball rotary jointand consists of at least one outer joint part having first ball racewaysthat run longitudinally, an inner joint part having second ball racewaysthat run longitudinally, and balls that transfer torque and are eachguided in first and second ball raceways that lie radially opposite oneanother. In this connection, the outer joint part is rigidly connectedwith the tubular shaft, and the inner joint part is rigidly connectedwith the shaft journal. The inside diameters of the outer joint part orof the subsequent tubular shaft, subsequent to the free space taken upby the inner joint part in operation, in the case of pushing movements,in the direction towards the tubular shaft, are configured to be smallerthan the outside diameter of the inner joint part.

With this configuration, the result is supposed to be achieved that incase of a “crash,” energy is reduced or absorbed by the longitudinalshaft, by means of friction and widening of the parts of the drive shaftthat are displaced into one another. It is a disadvantage, however, thatbending out of the longitudinal drive shaft can take place as a resultof forces acting during the crash.

Another solution of this type is described in German Patent No. DE 42 24201 C2, with which a longitudinal shaft in the drive train of a motorvehicle is configured so that the other parts of the longitudinal shaftremain undamaged by means of a connection between the inner joint partand the shaft journal, which connection is releasable at a predeterminedaxial force in the drive train. For this purpose, axial stopping meansare provided for the inner joint part, in the outer joint part, on whichmeans the inner joint part is supposed to support itself when theconnection between the inner joint part and the shaft journal isreleased, and the shaft journal is subsequently pushed through the innerjoint part.

In the same way, support is supposed to take place by an introductioncone in the outer joint part, or in a bottom part that follows it and isconnected with the outer joint part. It is emphasized as beingparticularly advantageous that a targeted axial force, deviating fromzero in a positive manner, having controlled energy absorption, can beadjusted by the means for absorbing friction work or deformation workwhen the shaft journal is axially pushed through the inner joint partand into the introduction cone.

This solution also has the disadvantage that in the case of an accident,this longitudinal drive shaft can also bend out and penetrate into thepassenger space, which can lead to injuries to the persons situated inthe passenger space. Furthermore, the maximal length of the crash pathis very disadvantageous in the case of this variant, since the shaftjournal cannot be selected to have simply any desired length, because inthe case of a shaft journal having a greater length, bending-criticalspeeds of the rotation of the longitudinal shaft occur, which also havea disadvantageous effect on the stability system of a longitudinal shaftconfigured in such a manner.

Furthermore, German Patent No. DE 199 43 880 C1 describes a drivearrangement with a longitudinal drive shaft and an intermediate bearing,which are used in motor vehicles.

This longitudinal drive shaft consists of a first shaft section having afirst joint, a second shaft section having a second joint, and a thirdjoint in the form of a homokinetic fixed joint, which connects the firstshaft section and the second shaft section, and comprises theintermediate bearing, which is assigned to the first shaft section, andadjacent to the fixed homokinetic joint, a roller bearing. With thisdrive arrangement, the smallest inside diameters of the outer jointpart, of the second shaft pipe, of the outer joint part of the joint,and of the shaft pipe that belongs to the second shaft section, aregreater than the greatest outside diameters of the first shaft sectionand of the roller bearing of the intermediate bearing.

With this arrangement, it is supposed to be possible for the two shaftsections to move into one another in the manner of a telescope,essentially without force, if the maximally permissible displacementpath of the first joint and of the second joint, in the axial direction,is exceeded, for example due to a frontal impact of the vehicle.

By means of the different dimensions of the functional parts of thedrive arrangement, in order to be able to telescope them, it isguaranteed that these parts will be pushed into one another, butsignificant force effects are required to initiate this process oftelescoping, and again it cannot be precluded that the longitudinaldrive shaft bends out.

SUMMARY OF THE INVENTION

The invention is therefore based on the task of further developing alongitudinal drive shaft for motor vehicles, in such a manner that inthe case of a crash, the individual function-determining components ofthe longitudinal drive shaft can be pushed into one another, anduncontrolled bending out of the shaft sections of the drive shaft isavoided.

This task is accomplished, according to the invention, by a longitudinaldrive shaft for motor vehicles, which serves to transfer a torque andconsists of two or more shaft sections that are connected with oneanother by way of an intermediate shaft or a journal, which in turn arerigidly connected with a shaft section.

The connection takes place by way of a homokinetic displacement jointdisposed with the first shaft section, into the ball hub of which theintermediate shaft/the journal is fitted. On the opposite side, theintermediate shaft is mounted in a sleeve that is rigidly connected withthe rotor of the second shaft section.

A center bearing provided between the two shaft sections is structuredand configured in such a manner that the intermediate shaft, or, if ajournal is used, are the carriers of the center bearing.

The second shaft section of the longitudinal drive shaft as well as thecenter bearing, here the roller bearing of the center bearing, aredimensioned and configured so that they can telescope into the interiorof the first shaft section in the case of a frontal impact, a crash, andthus it is assured that the entire longitudinal drive shaft and alsoindividual partial pieces of it no longer bend out.

The homokinetic displacement joint disposed in the first shaft sectionis rigidly connected with the outer pipe of the first shaft section, andthe outer joint ring and the ball hub of the homokinetic displacementjoint are configured with ball grooves on their inner and outer wall,respectively, in which balls are disposed, so that they are guided andrun around.

When a journal is used in place of an intermediate shaft, the journal isconnected towards the first shaft section with the homokineticdisplacement joint, and rigidly connected towards the second shaftsection directly with the second shaft section. This can take place bymeans of a weld, for example.

The journal is configured, in the direction of the second shaft section,with the greatest outside diameter that is adapted to the outsidediameter of the pipe of the second shaft section, and a rigid connectionis achieved by means of welding.

The homokinetic displacement joint is sealed off from the atmosphere, onthe one side, by means of a sealing cap and a sealing bellows, andprovided with a closure lid on the opposite side. This lid preventsforeign bodies from penetrating into the interior of the homokineticdisplacement joint, which cause contamination and therefore disruptionsin operation. At the same time, the lubricant cannot exit from theinterior of the homokinetic displacement joint.

This closure lid not only prevents exit of lubricant and entry ofharmful substances into the homokinetic displacement joint, but also isconfigured as a safety element, which possesses planned breaking pointsthat are destroyed in the event of an accident, and guarantees freetelescoping of the one shaft section into the other.

The closure lid is configured as a funnel-shaped molded part, possessesan outer collar with a subsequent guidance bevel, which makes atransition into the cylindrical part of the closure lid, which is closedoff on the end side by means of the planar part.

The planned breaking points of the closure lid are formed by theattachment of the closure lid to the first shaft section or to the innerwall of the pipe of the first shaft section, or, in a furtherembodiment, in the region of the transition from the cylindrical part ofthe closure lid to the planar part.

Aside from the function of sealing the homokinetic displacement jointand forming planned breaking points, the closure lid acts as a guideelement, in the case of a crash, in such a manner that the telescopedparts, the intermediate shaft or the journal, the roller bearing of thecenter bearing, and the balls, the cage, as well as the ball hub of thehomokinetic joint, are guided in the cylindrical part of the closurelid.

In this connection, it is advantageous that the homokinetic displacementjoint breaks down into its individual parts almost without force, andthat the planned breaking points lie outside of the displacement joint,so that aside from the destruction of the lid, unhindered telescoping ofthe functional parts that are displaced in the case of a crash is madepossible. This has a positive effect on the entire telescoping process,in its totality.

BRIEF DESCRIPTION OF THE DRAWINGS

Other objects and features of the present invention will become apparentfrom the following detailed description considered in connection withthe accompanying drawings. It is to be understood, however, that thedrawings are designed as an illustration only and not as a definition ofthe limits of the invention.

In the drawings, wherein similar reference characters denote similarelements throughout the several views:

FIG. 1 shows one embodiment of the longitudinal drive shaft in theoperating state;

FIG. 2 shows the longitudinal drive shaft in a first crash position;

FIG. 3 shows the longitudinal drive shaft in another crash position,with the first planned breaking point becoming active; and

FIG. 4 shows the longitudinal drive shaft in yet another crash position,with the second planned breaking point becoming active.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The configuration of one embodiment of the longitudinal drive shaft isshown in FIG. 1, in a fundamental representation. This consists of afirst and second shaft section 1, 2, which each consist of a pipe 3 and4, which are connected with one another by way of an intermediate shaft12 or configured as journals 16. The center bearing 6 is providedbetween the two shaft sections 1, 2; its roller bearing 7 is provided onintermediate shaft 12, to provide support, or, if a journal 16 is used,on the latter.

In the following, reference will only be made to an intermediate shaft.First shaft section 1 consists of pipe 3, in which or towards whichhomokinetic displacement joint 5 is disposed.

Homokinetic displacement joint 5 consists of a ball hub 8 that isdisposed on intermediate shaft 12, an outer joint ring 9, t cage 10, andball grooves, not shown in any detail, which are provided in outer jointring 9 and ball hub 8, in which balls 13 run.

On the right side, homokinetic displacement joint 5 is sealed off with asealing cap 15 and a sealing bellows, not shown in detail, and on theleft side of homokinetic displacement joint 5, a closure lid 11 thatfunctions as a securing element for the joint is provided.

Closure lid 11 is produced from a thin-walled material, for example ametal sheet, and configured as a shaped part. It consists of an outercircumferential collar 20 and a cylindrical part 17, which are connectedwith one another by a guidance bevel 19.

The end side of closure lid 11 is configured with a planar part 18,which seals off closure lid 11, and, in the installed state, homokineticdisplacement joint 5.

From FIG. 1, it is evident that closure lid 11 is connected with outerjoint ring 9 of homokinetic displacement joint 5. This connection pointrepresents a first planned breaking point 14, whose task it is toperform its function in the case of a crash, which means that here, theconnection between closure lid 11 and homokinetic displacement joint 5is dissolved or cancelled out, in order to allow telescoping of secondshaft section 2 into first shaft section 1.

A first position of the displacement of shaft section 2 in the directionof homokinetic displacement joint 5 is shown in FIG. 2, from which it isalso evident that shaft section 2 was already pushed so far to the leftthat roller bearing 7 was pressed out of center bearing 6, and theintermediate shaft as well as the ball hub bump against or come to lieagainst closure lid 11. During the displacement, an axial stress alsooccurred on homokinetic displacement joint 5, with the consequence thatthe ball hub 8 has moved out of outer joint ring 9 by a certain part,and intermediate shaft 12 has come to lie against the inside of theplanar part of closure lid 11.

In this position, the connection between closure lid 11 and homokineticdisplacement joint 5 still exists, as documented by the planned breakingpoint indicated with the number 14 in FIG. 2.

When shaft section 2 penetrates further into homokinetic displacementjoint 5, and subsequently, into the interior of pipe 3, planned breakingpoint 14 performs its function, in that the connection between closurelid 11 and homokinetic displacement joint 5 is interrupted.

FIG. 3 already shows the position in which telescoping of shaft section2 into shaft section 1 has proceeded to such an extent that balls 13have also exited from cage 10, and are situated in the intermediatespace between ball hub 8 and roller bearing 7 and thus cage 10.

From FIG. 3, it is also evident how closure lid 11 fulfills its guidancetask, in that closure lid 11 slides along the inner wall of pipe 3 byway of its outer collar 20, and thus imparts guidance to the telescopingfunctional elements, and bending out of the longitudinal drive shaft isprevented. FIG. 4 shows the second planned breaking point 14 of closurelid 11 going into effect. Here, closure lid 11 is configured in such amanner that planned breaking point 14 lies in the region of thetransition from cylindrical part 17 to planar part 18, and destructionof closure lid 11 also takes place at this point, as is evident fromFIG. 4.

In this connection, this planned breaking point 14 is dimensioned insuch a manner that ball hub 8 does not press the entire closure lid 11out of outer joint ring 9 of homokinetic displacement joint 5, butrather ball hub 8 punches out the front part, planar part 18 of closurelid 11, in the broadest sense, thereby the path is cleared for furtherdisplacement of the telescoping components. Here, cylindrical part 17 ofclosure lid 11 takes over the function of guiding these parts.

Accordingly, while only a few embodiments of the present invention havebeen shown and described, it is obvious that many changes andmodifications may be made thereunto without departing from the spiritand scope of the invention.

1. A longitudinal drive shaft for motor vehicles, for transferring atorque. comprising: at least two shaft sections comprising a first shaftsection and a second shaft section; an intermediate shaft or a journalconnecting the two shaft sections to each other; a center bearing havinga roller bearing and being carried by the intermediate shaft or journal;a homokinetic displacement joint rigidly disposed in a pipe forconnecting the intermediate shaft or journal to the first shaft section,said joint comprising an outer joint ring, a ball hub, balls which runguided in ball grooves of the outer joint ring and ball hub, and a cage;a sealing cap and a sealing bellows for sealing the joint in a directionof the second shaft section, and a closure lid assigned to the joint andconfigured as a guidance and securing element, said lid being disposedtowards the first shaft section and projecting into an interior of thepipe, wherein parts of the center bearing and the second shaft sectionthat are displaced during a crash are configured to be smaller than aninside diameter of the pipe, and wherein an inside diameter of the outerjoint ring is greater than outside diameters of the roller bearing andof the pipe.
 2. A longitudinal drive shaft according to claim 1, whereinthe closure lid is rigidly connected with the outer joint ring.
 3. Alongitudinal drive shaft according to claim 1, wherein the closure lidis a shaped part produced from a thin-walled material, and consists ofan attachment collar, a cylindrical part, a planar part, and a guidancebevel, and is configured with planned breaking points.
 4. A longitudinaldrive shaft according to claim 2, wherein a connection point of theclosure lid to the outer joint ring is configured as a planned breakingpoint.
 5. A longitudinal drive shaft according to claim 3, wherein atransition point from the cylindrical part to the planar part of theclosure lid is configured as a planned breaking point.
 6. A longitudinaldrive shaft according to claim 3, wherein the cylindrical part of theclosure lid guides components that telescope into the interior of thepipe during a crash, and wherein the guidance bevel is configured as anintroduction cone.
 7. A longitudinal drive shaft according to claim 1,wherein the closure lid is rigidly connected with an inner wall of thepipe.
 8. A longitudinal drive shaft according to claim 1, wherein thejournal is configured with an enlarged outer diameter on one side, whichcorresponds to a diameter of the pipe, and wherein the journal isrigidly welded to the pipe.